Synchronizing system



1, 1939- H. IL. SEELEY 2,168,175

SYNCHRONIZING SYSTEM Filed Oct. 11, 1938 Inventor: Harold T Seeley,

H is Att Ofh ey.

Patented Aug. 1, 1939 UNITED STATES PATENT OFFICE SYNCHRONIZING SYSTEMNew York Application October 11, 1938, Serial No. 234,431

6 Claims.

My invention relates to synchronizing systems for controlling theclosing of a circuit breaker between two alternating current circuitsand particularly to an improved arrangement for initiating the closingoperation of the circuit breaker at substantially the same phase anglebetween the voltages of the two circuits for all frequency differencesbelow a predetermined value.

My invention is particularly applicable for use in synchronizing systemsof the type disclosed and claimed in United States Letters Patent1,852,825, granted April 5, 1932, on an application filed by me andassigned to the same assignee as this application. In the aforesaidLetters Patent the alternating current generator is excited so as toproduce a voltage reasonably free from variations in magnitude due toprevious magnetizations of the generator but not high enough to causethe motor to pull into synchromsm and then, while maintaining thesubnormal excitation, the generator is connected to the alternatingcurrent system during a predetermined range of the voltages of thegenerator and system if frequency difference is less than thepredetermined value. In the embodiment of the invention disclosed in theaforesaid patent the closing operation of the circuit breaker betweenthe generator and the alternating current system is initiated atdifferent points within a 180 phase angle range of the generator andsystem voltages depending upon the frequency difference. For example, atthe maximum frequency difference at which the synchronizing arrangementwill effect the closing of the circuit breaker the closing operation isinitiated at an angle substantially at the end of the 180 phase anglerange, whereas, if the frequency difference is substantially zero, theclosing operation is initiated at an angle substantially at thebeginning of the 180 phase angle range.

One object of my present invention is to provide an arrangement wherebythe closing indication is given at substantially the same angle in thephase angle range irrespective of the frequency difference so long as itis below a predetermined value.

My invention will be better understood from the following descriptionwhen taken in connection with the accompanying drawing, Fig. l

or" which shows diagrammatically an automatic synchronizing arrangementembodying my invention, Fig. 2 of which discloses a modification of aportion of the arrangement shown in Fig. l, and its scope will bepointed out in the appended claims.

Referring to Fig. 1 of the drawing, 1 represents a polyphase generatorwhich is adapted to be connected to a polyphase circuit 2 by means of acircuit breaker 3 which may be of any suitable type examples of whichare well known in the 5 art. The generator I may be driven by anysuitable type of prime mover, not shown.

For controlling the excitation of the generator I a suitable source ofdirectcurrent, shown as an exciter 4 directly connected to the generator10 I, is provided. The field winding of the generator I is arranged tobe connected to the ter minals of the exciter I by means of a suitablecontrol switch 6 which may be operated either manually or automatically.In the particular 15 embodiment of my invention, shown in Fig. l, theamount of direct current supplied to the generator field winding, whilethe switch 6 is closed and the circuit breaker 3 is open, is justsuflicient to produce a voltage across the gen- 20 erator terminalswhich is reasonably free from variations in magnitude due to previousmagnetizations of the generator field structure but is not sufiicient topull the generator into synchronism when it is connected to the circuit2. 25 In the arrangement shown, the desired subnormal excitation isobtained by connecting suitable current limiting means, such as aresistor l, in series with the exciter 4 and the generator fieldWinding.

For efiecting the closing of the circuit breaker 3 at substantially thesame phase angle between the voltages of the generator I and the circuit2 at all frequency differences below a predetermined value, I provide aphase responsive 35 relay 8 comprising an induction disk l3 which hasopposing torques exerted thereon by the shaded pole motor elements l4and I5. Suitable means, such as a drag magnet i6, is provided to exert aretarding force on the disk I3 40 so that the desired time delay actionin the movement of the disk i3 may be obtained. Attached to the disk I3is a contact member ll which is arranged to be moved into engagementwith the stationary contacts is after the torque 46 of the motor element[4 has exceeded the torque of the motor element l5 for a time intervaldetermined by the drag magnet 16. When the torque of the motor elementl5 exceeds the torque of the motor element M, the contact 50 member I"!is arranged to be moved in the opposite direction so as to engage thestationary stop I9.

The motor element 14 is energized by the windings 20 and 2| which arerespectively con- 55 nected to the circuit 2 and the generator I so thata torque is exerted on the disk 13 in accordance with the vectordifference between the voltages of the circuit 2 and the generator l andin a direction to move the contact member if into engagement withcontacts 18. The motor element I5 is provided with the windings 22 and23 which are respectively energized by the same voltages which energizethe windings 2E! and 2! of the motor element I4. The windings 22 and 23are so arranged that they exert a torque on the disk [3 in accordancewith the vector sum of the voltages impressed thereon and in a directionto move the contact member it away from the contacts [8. The motorelements [4 and 15 are preferably arranged so that during each cycle offrequency difference between the voltages of the circuit 2 andthegenerator l, a resultant torque in the direction to close thecontacts [8 is produced during approximately a phase angle range of thevoltages, and during the remaining approximately 190 phase angle rangeof the voltages a resultant torque is exerted on the disk I3 in adirection to maintain the contact member I! out of engagement with thecontacts l8. Therefore, the average resultant torque during each cycleof frequency difference is in a direction to maintain the contacts I8open. Due to the retarding effect exerted by the drag magnet 56, it willbe observed that only when the frequency difference between the voltagesof the generator I and the circuit 2 is less than a predetermined valuewill the resultant torque in a direction to close the contacts l8 beexerted for a sufiicient .length of time to accomplish this result.

It will be observed, however, that the phase angle at which the contacts[8 close Varies with the frequency difference, but after being closed,they are opened at substantially the same phase angle irrespective ofthe frequency difference because as soon as the torque exerted by themotor element l5 predominates, and this occurs at substantially the samephase angle for all frequency differences, the contact member I!immediately moves out of engagement with contacts l8 because the dragmagnet i6 has very little retarding effect during the slight movement ofthe disk !3 required to separate the contacts i1 and I8. Therefore, ifthe motor element I4 is designed so that its torque predominates overthe torque of motor element 55 during the phase angle range during whichthe voltages are more than 90 apart, the contacts [8 will always open atapproximately 90 ahead of phase coincidence.

In accordance with my present invention, I make use of this opening ofthe contacts IS at substantially the same phase angle at all frequencydifferences to initiate the closing operation of the circuit breaker 3.

In the arrangement shown in Fig. l, the closing of the contacts [8effects the energization of a control relay 24 which in turn effects theenergization of a second control relay 25 which completes a lockingcircuit'for itself independently of the contacts E8 of relay 3 and thecontacts 3i of control relay 24. Then, when the contacts l8 aresubsequently opened so that the relay Z4 is deenergized, a circuit iscompleted for the closing coil 9 of the circuit breaker 3 through seriesconnected contacts of the deenergized control relay 2 and the energizedcontrol relay 25.

After the circuit breaker 3 is closed to connect the generator I to thecircuit 2, it is desirable to increase the excitation of the generatorto itsnorrnal value so as to pull the generator into synchronism. In thearrangement shown in the drawing this result is accomplished byproviding the circuit breaker 3 with the auxiliary contacts 26 whichshort-circuit the resistor 1 in the field circuit of the generator Iwhen the circuit breaker 3 is closed.

Since the windings 2! and 23 of the phase responsive relay 8 areconnected so that they are energized by the relatively low voltage ofthe generator I prior to the closing of the circuit breaker 3, it isnecessary to protect these windings against the relatively high voltagewhich would be applied to them in response to the closing of the circuitbreaker 3. In the arrangement shown in the drawing, this protection isobtained by connecting the auxiliary contacts 35 of the circuit breaker3 in the energizing circuit of the windings 2i and 23 so that thiscircuit is interrupted by the closing of the circuit breaker 3.

In order to prevent the voltage induced in'the generator field windingfrom rising to a dangercus value when the circuit breaker 3 is closed, Iconnect, by means of the auxiliary contacts 2! of circuit breaker 3, adischarge resistor 28 across the terminals of the generator fieldwinding. Preferably the contacts 27 are arranged in a manner well knownin the art so as to overlap the contacts 25 so that the contacts 26 areclosed before the contacts 21 are opened and vice versa.

The operation of the arrangement shown in Fig. 1 of the drawing is asfollows: When it is desired to place the generator l in operation, it isfirst brought up to approximately synchronous speed by controlling thespeed of the prime mover which drives it and then the field switch 6 isclosed so that a sufficient direct current flows through the generatorfield winding to produce the desired subnormal generator voltage. Whenthe generator voltage builds up to this predetermined subnormal valueand the frequency difference between this subnormal voltage and thevoltage of the circuit 2 is less'than a predetermined value, the relay 8closes its contacts I8 at some predetermined phase angle in the 180phase angle range during which the torque exerted by the motor elementI4 predominates over the torque exerted by the motor element I5 andmaintains these contacts l8 closed until the end of this phase anglerange. contacts l8 completes across the exciter through the auxiliarycontacts 30 on the circuit breaker 3 an energizing circuit for thecontrol relay 24 which in turn by closing its contacts 3! completesacross the exciter an energizing circuit for the control relay 25through the auxiliary contacts 30 on the circuit breaker 3. By closingits contacts 32 relay 25 completes a locking circuit for itself aroundthe contacts 3! of the relay 24. When the relay 8 opens its contacts l8and thereby deenergizes the control relay 24, an energizing circuit iscompleted across the exciter for the closing coil 9 of the circuitbreaker 3 through the contacts 33 of the deenergized control relay 24and the contacts 34 of the energized control relay 25 so that thesubnormally excited generator is connected across the circuit 2. Byopening its contacts 35 the circuit breaker 3 interrupts the circuit ofthe low voltage windings 2| and 23 of the relay 8 and by opening itscontacts 30 interrupts the holding circuit of the control relay 25. Byclosing its auxiliary contacts 25, the circuit breaker 3 short-circuitsthe resistor I so that the excitation of the generator I builds up toits normal value and causes the generator The closing of the 1 to pullinto synchronism, and then by opening its contacts 21, the dischargeresistor 28 is disconnected from across the terminals of the generatorfield winding.

In the modification shown in Fig. 2 the closing of the contact 3! of thecontrol relay 24 when it is energized in response tothe closing of thecontacts E8 of the relay 8 connects the winding of the control relay 25in parallel with the contacts [8 so that, when these contacts aresubsequently opened, the relay 25' becomes energized and by closing itscontacts 34' completes an energizing circuit for the closing coil 9 ofthe circuit breaker 3.

While I have, in accordance with the patent statutes, shown anddescribed my invention as applied to a particular system and asembodying various devices diagrammatically indicated, changes andmodifications will be obvious tothose skilled in the art, and Itherefore aim in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An arrangement for closing a circuit breaker in response to the phaserelation between the voltages of two alternating current circuitscomprising contacts having a normal condition and a second condition, amovable member for changing said contacts from one condition to theother, means energized from said circuits for exerting on said memberduring a predetermined phase range of the voltages of said circuits atorque in a direction to change said contacts to said second conditionand a torque in the opposite direction during the remaining phase rangeof said voltages, means for controlling the movement of said member insaid first mentioned direction so that said contacts are changed to saidsecond condition only when the frequency difference between saidvoltages is less than a predetermined value, and means dependent upon.said contacts being in said second condition and subsequently out ofsaid second condition for effecting the closing operation of the circuitbreaker.

2. An arrangement for closing a circuit breaker in response to the phaserelation between the voltages of two alternating current circuitscomprising normally open contacts, a movable member for closing saidcontacts when moved a predetermined distance in a predetermineddirection, means energized from said circuits for exerting on saidmember during a predetermined phase range of the voltages of saidcircuits a torque in a direction to close said contacts and in theopposite direction during the remaining phase range of said voltages,means for delaying the movement of said member in said contact closingdirection whereby said contacts are closed only when the frequencydifference between said voltages is less than a predetermined value, andmeans dependent upon the closing and the subsequent opening of saidcontacts for effecting the closing operation of the circuit breaker.

3. An arrangement for closing a circuit breaker in response to the phaserelation between the voltages of two alternating current circuitscomprising normally open contacts, a movable member for closing saidcontacts when moved a predetermined. distance in a predetermineddirection, means energized from said circuits for exerting on saidmember during a predetermined phase range of the voltages of saidcircuits a torque in a direction to close said contacts and in theopposite direction during the remaining phase range of said voltages,means for delaying the movement of said member in said contact closingdirection whereby said contacts are ciosed only when the frequencydifference between said voltages is less than a predetermined value, arelay, means responsive to the closing of said contacts for energizingsaid relay, and means responsive to the opening of said contacts whilesaid relay is energized for closing said circuit breaker.

4. An arrangement for closing a circuit breaker in response to the phaserelation between the voltages of two alternating current circuitscomprising normally open contacts, a movable member for closing saidcontacts when moved a predetermined distance in a predetermineddirection, means energized from said circuits for exerting on saidmember during a predetermined phase range of the voltages of saidcircuits a torque in a direction to close said contacts and in theopposite direction during the remaining phase range of said voltages,means for delaying the movement of said member in said contact closingdirection whereby said contacts are closed only when the frequencydifierence between said voltages is less than a predetermined value, arelay, means responsive to the closing of said contacts for energizingsaid relay, means for maintaining said relay in its energized positionwhen said contacts are subsequently opened, and means responsive to theopening of said contacts while said relay is energized for closing saidcircuit breaker.

5. An arrangement for closing a circuit breaker in response to the phaserelation between the voltages of two alternating current circuitscomprising normally open contacts, a movable member for closing saidcontacts when moved a predetermined distance in a predetermineddirection, means energized from said circuits for exerting on saidmember during a predetermined phase range of the voltages of saidcircuits a torque in a direction to close said contacts and in theopposite direction during the remaining phase range of said voltages,means for delaying the movement of said member in said contact closingdirection whereby said contacts are closed only when the frequencydifference between said voltages is less than a predetermined value, anauxiliary relay, an energizing circuit for said relay including saidcontacts, a second auxiliary relay, means responsive to the energizationof said first mentioned auxiliary relay for effecting the energizationof said second auxiliary relay, a locking circuit for said second relayfor maintaining said second relay energized independently of said firstmentioned relay, and means responsive to the deenergization of saidfirst mentioned relay while said second relay is energized for closingsaid circuit breaker.

6. An arrangement for closing a circuit breaker in response to the phaserelation between the voltages of two alternating current circuitscomprising normally open contacts, a movable member for closing saidcontacts when moved a predetermined distance in a predetermineddirection, means energized from said circuits for exerting on saidmember during a predetermined phase range of the voltages of saidcircuits a torque in a direction to close said contacts and in theopposite direction during the remaining phase range of said voltages,means for delaying the movement of said member in said contact closingdirection whereby said contacts are closed tacts whereby said relays areenergized in series in response to the subsequent opening of saidcontacts, and means responsive to the energization of said secondauxiliary relay for effecting .the closing of said circuit breaker.

HAROLD T. SEELEY.

